Power suit: Researcher weaves nanogenerators into fabrics

PORTLAND, Ore.  Clothing fabrics that generate electricity from the motion of wearing them have been described by researchers at the Georgia Institute of Technology.

The inventor, Georgia Tech professor Zhong Lin Wang, has previously described nanogenerators--arrays of nanowires that produce as much as 4 watts/cm3--for powering small electronic devices or to recharge batteries. Wang has also designed nanogenerators to power self-contained sensors that harvest environmental energy thereby eliminating the need for batteries.

Alternating pairs of fibers with zinc oxide bristles rub against each other to generate electricity.

Wang's latest invention--fabrics that generate energy from the wearer's motion--are the furthest from commercialization. Besides clothing, the nanogenerating fibers could also be woven into curtains, tents or other structures that capture energy from wind, sound vibration or other mechanical energy.

"The first commercial application of nanogenerators will be self-powered nanodevices--probably for powering gas and pressure sensors," said Wang. "Powering personal electronics with wearable fabric will likely be the last application of my nanogenerators to be commercialized."

The basic concept involves weaving together two types of zinc oxide nanowires to harness the piezoelectric effect when the fibers flex--producing as much as four nano-amperes at an output voltage of about four millivolts. The fibers themselves measure 1-centimeter long.

The experimental fabric now being tested was woven from Kevlar fibers. Zinc oxide nanowires were grown radially out of a polymer (tetraethoxysilane) that holds them in place. The 3.5-micron-long fibers are spaced several hundred nanometers apart. One bristling fiber in each pair was coated with gold to serve as the electrode and to deflect nanowire tips on the other fiber.

"The two fibers scrub together" said Wang. "The piezoelectric-semiconductor process converts
their mechanical motion into electrical energy." He collaborated with Georgia Tech researcher Xudong Wang and Yong Qin.